Automatic center punch and the like



March 9, 1965 J. A. FREY ATOMATIC CENTER PUNCH AND THE LIKE Filed June 21. 1963 FIGB mvENToR, JOHN A. FREY,

ATTORNU.

United States Patent O 3,172,204 AUTOMATIC CENTER PUNCH AND THE LIKE John A. Frey, 82S Holiyhock Lane, Orange, Conn. Filed June 21, 1963, Ser. No. 289,527 1 Ciainr. (Ci. 341-367) The present invention relates to an improved springpowered, automatic center punch of the type including a slidable pointed bit extending partly out of a generally tubular casing which houses a hammer adapted to be biased by spring means to offer a blow, actuated by a v`plunger which is intermediate said bit and hammer; the tool being operated by setting the point on that point of an object to be marked with a dent and then upon pushing the casing towards such object, the hammer is caused to be biased and then released by a camming action causing the plunger to enter a socket in the harnmer, whereupon the hammer imparts a blow which is transmitted to the pointed bit.

An object of this invention is to provide a novel and improved automatic center punch of the class mentioned, in which the points of impact on the plunger and pointed bit, change from blow to blow so that there occurs no undue wearing away of parts and thus the tool is given a long life. l

Another object thereof is to provide a novel and improved automatic center punch construction of the character described, in which all the parts, except the springs, are screw machine products, thereby materially decreasing the cost of manufacture. Another object of this invention is to provide a novel and improved automatic center punch of the type set forth which does not miss to operate and hence the tool has 100% reliability.

Still a further object thereof is to provide a novel and improved center-punch tool of the nature described, having the mentioned attributes, and which is easy to use and most eihcient in carrying out the purpose for which it is designed.

Other objects and advantages will become apparent as this disclosure proceeds.

For the practice of this invention, a ball is interposed between the plunger and the butt end of the pointed bit and such ball is in contact with both of them. That end of the plunger which contacts said ball, is semi-spherical and in the particular embodiment herein illustrated, the butt end of the pointed bit, is also semi-spherical as most advantageous, though the tool will work even if the butt end of said bit is made flat. The diameter of the ball is preferably slightly larger than the diameter of said semispherical surfaces and in such relation to the bore it is in, that the plunger which is spring-biased towards the ball, shall normally be out of alignment with the longitudinal axis of the tool and slanted in relation therewith.

In the accompanying drawing forming a part of this specification, similar characters of reference indicate corresponding parts in all the views.

FIG. l is a central longitudinal section of an automatic center punch embodying the teachings of this invention. The tool is here shown in its normal rest condition, set on a piece to be marked.

FIG. 2 is a view like FIG. 1, but here the tool is shown being pressed on whereby the pointed bit is retracted and the hammer is readied to impart a blow.

FIG. 3 is a view like FIG. 1, showing the condition of the tool at the time the blow is given, whereupon the pointed bit is caused to make a dent in the piece of work.

In the drawing, the numeral designates generally an automatic center punch which is a preferred embodiment of this invention, where all parts are of circular cross section and hence easily made as screw machine prod- 3,172,204 Patented Mar. 9, 1965 ucts. This tool comprises an elongated tubular casing denoted generally by the numeral 16, which houses an elongated plunger 17 between an unattached ball 18 and a slidable hammer member 19, and also has a retractable pointed bit 20; said ball being between said plunger and pointed bit. A compression coil spring 21 biases said hammer member 19 towards said plunger and forces said hammer member to normally rest against a seat 22. A second compression coil spring 23, biases said plunger V17 against said ball 18, and hence said ball bears against the butt end head 24 of said pointed bit.

The casing 15 consists of the tubular member 2S, which at hammer-end is closed by a cap 26, serving as an anchor for the coil'spring 21 which bears against said hammer member 19, and said tubular member 25 has an extension 27 at its other end which serves as the slide bearing for the pointed bit 20; said cap and extension, being threadedly engaged to the respective ends of said tubular member 25, to permit adjustment of the initial stress in said springs 21 and 23 respectively. Said member 25 has a constricted passage 28 intermediate its ends, thereby oliering the seat 22, and as an anchorage for the coil spring 23, the seat 29. The constriction 28 is of circular cross section and is co-axial with the hammer member 19, the latters socket31, and the bit 2i). The head 32 of the plunger 17 which bears against 'the ball 18, and the distal end of the head 24 of the bit 20, are semi-spherical in shape and of a diameter preferably slightly less than that ofthe ball 18. The diameter of said ball must be such in relation to the diameter of the bore 33 Vit is in, that the plunger 17 and the bit 20 shall never contact each other. It is best that the balls diameter be more than the radius of said bore '33. It is essential that dimensions Vbe so chosen that when the tool 1S is in normal rest condition as shown in FIG. l, the plunger 17 shall be slanted to the axis line of the hammer member 19 and preferably bear against the wall of the constricted passage 28. It is suggested that the diameter of said ball 18 shall be a minimum of 10% larger than the radius of said bore 33 and a minimum of 10% smaller than the diameter of said bore.

The plunger 17, near head end, has a flange 34 to seat the coil spring 23, and from there, has three successive sections indicated by the numerals 35, 36 and 37 respectively. The section 3S is of a diameter adapted to slidably tit in the constricted passage 28. The stern section 37 is of a reduced diameter adapted to slidably t into the hammers socket 31. The section 36 is frustoconical and merges with said other sections. The spring 23 which biases the plunger 17, is relatively weak as compared with the comparatively strong spring 21 which biases the hammer member 19.

To operate the tool 15, it is set so that the point of the bit 20 is on that point on the surface 33 of a piece of work, which is to be dented. The tool is in the condition shown in FIG. 1. Now, the casing 16 is pressed towards the work, whereupon as shown in FIG. 2, more of the bit 20 will move into the casing, thereby causing the plunger 17 to shift against the hammer member 19, and move it away from the seat 22. Both springs 21 and 23 will become compressed and upon continuing such movement of the casing, the plunger 17 will be cammed and get into alignment with the hammer member 19, whereupon the hammer will be freed to be forced by the fully stressed spring 21, to move towards the bit 20, because the plunger section 37 will enter the socket 31 and receive the hammers blow as shown in FIG. 3. The impact will be transmitted to the bit and the work will be dented, because the point will have entered the work as shown at 4). Upon removal of the tool, the stressed spring 23 will restore the plunger 17, and hence also the ball 1S and the bit 20, to normal rest position as shown in FIG. 1, and the tool will then again be ready for its next use.

When as in FIG. 3, the plunger 17 comes into axial alignment with the hammer 19, the ball 18 is never in such alignment, and it is found that upon every operation of this tool 15, that said ball 18 will receive some turning movement and change its position along the wall of the bore 33. Hence, the points of impact of said ball and plunger head 32 and the points of impact of said ball and the bits head 24, change from one stroke of the tool to the next, thereby eliminating wear on just definite points as was the experience in prior devices of this class.

It is to be particularly noted that the ball 18 will always position the plunger 17 off center and to a slant position as shown in FIG. 1, when the pointed bit 26 extends its maximum out of the casing 16, and such action is not etfected when the butt end of said bit is at instead of semi-spherical as herein shown.

This invention is capable of numerous forms and various applications without departing from the essential features herein disclosed. It is therefore intended and desired that the embodiment shown herein shall be deemed merely illustrative and not restrictive and that the patent shall cover all patentable novelty herein set forth; reference being had to the following claim rather than to the specic description herein to indicate the scope of this invention.

I claim:

In an automatic center punch or the like, rcomprising a tubular casing having a constriction intermediate its ends forming a camming element, a bit slidable in said casing at one side of said constriction and protruding from said casing; said bit having a rst semi-spherical head at its end which is interior said casing; said casing at said one side of said constriction, being of circular cross-section internally, a separate ball within said casing,

bearing against said rst semi-spherical head, a plunger of circular cross-section including a second semi-spherical head bearing against said ball, a stem extending into said constriction and a tapered cam portion on said stem, adapted as said stem is urged through said constriction, to engage said camrning element and move the extremity of said stem remote from said second semi-spherical head, from a position offset with respect to the axis of said casing, to a substantially centered position in alignment with the longitudinal axis of said casing, a hammer member slidable in said casing on the opposite side of said constriction, a spring biasing said hammer member towards said constriction; the inward end of said hammer member being adapted to be engaged by said stem when in its offset position and a socket in said inward end of said hammer member, adapted to receiver said stem when said stem is in its aligned position whereby on receiving said stem, the hammer member is driven by said spring into impact engagement therewith and a spring biasing said plunger towards said ball; the dif ameter of said ball being smaller than the diameter of said cross-section of the casing and larger than the diameters of said semi-spherical heads respectively; said ball being of a diameter so that said plunger remains spaced from said bit.

FOREIGN PATENTS 514,924 11/20 France.

WILLIAM FELDMAN, Primary Examiner.

MILTON R. MEHR, M. I-IENSON WOOD, IR.,

Examiners. 

